- Can you use Google hreflang to international SEO? Yes
- If you have problems with duplicate content, should you then combine hreflang with canonical?Yes
- If you do NOT have problems with duplicate content, should you then also combine hreflang with canonical? No
Finally I should like to say that earlier it was not a good idea to let the three sub domains or equivalent ccTLD’s be indexed in Google, because of the problems with double content. At the same time it would be almost impossible to get other than the main .com domain to appear in all search results, even when searching in Google’s country-specific indexes. But thanks to hreflang and canonical, this is now possible.